Research On The Fabrication Of Flexible Micro/nano Patterned Substrates And Their Application In Surface Enhance Raman Scattering

At present,the traditional hard-surface enhanced Raman scattering(SERS)substrate could not fit closely with the surface with curvature,which made it difficult to extract the analyte under test.Therefore,it is very important to prepare a flexible SERS substrate which can be closely fitted to the curved surface and has good bending resistance.Polydimethylsiloxane(PDMS)has been widely used to prepare SERS substrate due to its adhesiveness,stretchability and optical transparency.At present,various micro-nano patterns can be prepared by using lithography,electron beam etching and other technologies and then transferred to the PDMS surface to prepare flexible micro-nano patterns substrate,and then the physical deposition of precious metals on the surface for SERS,but these technologies are complex and require expensive processing equipment.However,micro-nano wrinkles can be self-assembled on the PDMS surface to prepare micro-nano wrinkle substrates by adopting simple,low-cost thermal expansion and prestretching methods.However,the prepared wrinkles do not have good time stability and bending resistance,which will prevent the SERS substrate prepared from being placed for a long time and bring inconvenience to practical application.In order to solve the above problems,this paper used the trend of nanowires in copper nanowires network and the gap between nanospheres in SiO2 stacking structure to form pseudo-periodic micro-nano wrinkles with different morphologies on the surface of PDMS to prepare micro-nano wrinkle substrates.Among them,nanowires will support the wrinkle morphology of PDMS surface,and the nano-spheres will restrict the wrinkles on PDMS surface,so as to enhance the time stability and bending resistance of micro-nano wrinkle substrates.Physical deposition of precious metals on the substrates has been successfully used to prepare flexible SERS substrates.The research contents and results are as follows:1.A method of forming wrinkles on PDMS surface using copper nanowire network was presented and implemented.Copper nanowires(average diameter of 50-200 nm,length of 10-30 μm)repeatedly drops(number 7)on the glass forming nanowires network,then the flow of PDMS to fill the gap to the nanowires and attached to the glass substrate,and solidified(slow speed:60℃,18 h;Rapid:100℃,0.5 h)after the PDMS was removed from the glass substrate,and finally with the help of the copper nanowire network transferred to PDMS,pseudo-periodic miciro-nano wrinkles of different morphologies were formed on the surface of PDMS in contact with the glass substrate.2.A method of forming wrinkles on PDMS surface using SiO2 nanosphere was proposed and implemented.SiO2 nanosphere with a diameter of 300 nm was used to form a compact stacking structure,in which the nanosphere with a diameter of 300 nm was easily removed by PDMS and the compact stacking structure was simply and quickly prepared.Then,the flowing PDMS were filled into the gap of the nanospheres and attached to the Si substrate.After heating and curing at 100℃ for 20 minutes,the PDMS was removed from the Si substrate.Finally,with the help of the nanosphere transferred to the PDMS film,pseudo-periodic micro-nano wrinkles were formed on the surface of PDMS film in contact with the Si substrate.3.The 60 nm precious metal Au was deposited on the flexible wrinkle substrate with nanospheres by magnetron sputtering to form a rough Au film.The ridges of the wrinkles and the gaps of adjacent ridges could act as hot-spots and generate high-intensity local electromagnetic fields,thus achieving high sensitivity SERS detection.Using rhodamine(R6G)as the probe molecule base for the study,the SERS enhanced characteristic showed that the detection limit could reach 10-10 M.Although,the time stability and bending resistance of the base showed that after R6G was added,the SERS were placed in the air for 31 days,and the signal strength of the characteristic peak at 1360 cm-1 decreased by 44.3%.After 1000 apple pasting,the signal strength at 1360 cm-1 was reduced by 40%after R6G was added.However,it was still better than the flexible SERS base prepared by thermal expansion wrinkle,with stronger time stability.